The electrical heart activity is usually characterized by employing a multitude of electrode pairs, each pair providing a potential difference called a lead. Each lead is considered to represent the electrical activity of the heart from a different spatial angle. A 12-lead ECG is frequently used. The potential changes are plotted against time in the electrocardiogram. The heart activity as seen in an electrocardiogram (ECG) signal is regularly composed of three main components: P-wave, QRS wave complex, and T-wave, wherein the first component is associated with the atrial activity (AA) and the last two components with the ventricular activity (VA) (see FIG. 1). Analysis of the ECG and locating P-waves in the ECG signal are a crucial task in identifying arrhythmias and in diagnosing them, including, for example, differentiating between supra-ventricular arrhythmia and ventricular arrhythmia. Various methods have been proposed for detecting ECG components, but the detection of the P-waves is still an unsolved problem. P waves may be hidden in QRS complexes or T waves, and the AA is relatively difficult to detect since the VA has much more energy. It is known that misdiagnosis rate in arrhythmias may go as high as 30% [Shiovich A. et al.: Am. J. Med. Sci. 340 (2010) 271-5]. The cardiologist is often forced to insert electrodes into the patient's body to obtain the missing information.
Various approaches of atrial extraction from ECG signals include techniques of average beat subtraction (when improved methods comprise spatiotemporal QRST cancellation), localized search area (searching for P wave outside the QRS-T complexes), blind source separation (Independent Component Analysis—ICA). Principal Component Analysis (PCA), and semi-invasive approaches. The different approaches have different shortcomings; the average beat subtraction relies on the assumption of fixed shape QRS complexes, the ICA and PCA methods rely on the independency of the sources (non-correlatedness in PCA), and the localized search relies on the assumption that the QRS or T wave do not hide the P wave. It is therefore an object of the invention to locate P-waves along the ECG without invasive techniques, only from the surface measurements.
It is another object of the invention to provide an ECG signal with marked or emphasized P-waves, thereby assisting the professional in arriving to a correct diagnosis, particularly in regard to subjects suffering with arrhythmia.
It is a still further object of the invention to simplify the ECG measurement process.
Other objects and advantages of present invention will appear as description proceeds.